1. Field of the Invention
The present invention concerns a process for producing acyclic nucleosides, such as, particularly, acyclovir of the below-mentioned formula (IV) and ganciclovir of the below-mentioned formula (V), both being an anti-viral agent. Acyclovir and ganciclovir are compounds having a powerful anti-viral activity, particularly, to herpes virus both in vitro and in vivo, and have already been authorized and sold commercially as an anti-viral chemotherapeutical agent.
2. Discussion of the Background
For the purpose of producing acyclovir or ganciclovir, there has been known, for example, a method of using guanine as a starting material or a method of using 2,6-dichloropurine or 2-amino-6-chloropurine. However, each of the methods has drawbacks in that the desired compound can not be obtained in a high yield, the desired compound can not be obtained easily in a high purity, and the procedures concerned are complicated from the industrial point of view. U.S. Pat. No. 4,199,574; J. R. Barrio et al., J. Med. Chem., 23 572 (1980); and J. C. Martin et al., J. Med. Chem., 26, 759, (1983) .
On the other hand, ribonucleosides such as guanosine, adenosine and inosine have been mass-produced by a fermentation process. In view of the above, it has been an important subject to develop a novel and industrially advantageous process for synthesizing acyclic nucleosides such as acyclovir and ganciclovir from the above-mentioned ribonucleosides.